This invention relates to a magnetic bearing assembly and a container device for mounting and protecting magnetic bearings.
Active electromagnetic bearings are used, for example, to support a rotor in a compressor or to replace oil lubricated bearings in turbomachinery. The active electromagnetic bearings are relatively expensive and require a control system to control power to the electromagnets. There is ongoing research to develop active electromagnetic bearings for application in sealless pumps.
Passive magnetic bearings have not been used for industrial equipment because passive magnetic bearings inherently have no damping properties and, as such, are not suitable for application in dynamic industrial equipment such as compressors, turbines, pumps, motors and other rotating equipment. Normally, these type of industrial equipment applications utilize a "hydrodynamic bearing" system in which damping is provided by a hydrodynamic film. In a sealless pump application, for example, the hydrodynamic fluid is the product being pumped. However, the pumped product provides poor lubrication properties, i.e., low viscosity and relatively high vapor pressure. A problem with product lubricated bearings in sealless pumps is that the pumps readily break down due to bearing damage resulting from the poor lubricating properties of the product.
Heretofore, a combination of a hydrodynamic bearing and a passive magnetic bearing has not been used. It is desired, therefore, to enhance the load carrying capacity of product lubricated hydrodynamic bearings by incorporating a passive magnetic bearing into the hydrodynamic bearing system.
Also, heretofore, it was not possible to use passive magnetic bearings in a corrosive environment because the magnetic material would degrade in contact with the corrosive fluid. It is desired therefore to provide a housing or container to protect the magnetic material and allow the operation of the magnetic bearings in a corrosive environment.
It is further desired to provide a container that will compensate for differing thermal growths and pressure differentials when in operation. It is desired that the volume inside the container walls remain unchanged despite differing thermal growths and pressure differentials across the container walls.
In prior art hydrodynamic bearings systems, a journal and bearing are separated by a hydrodynamic film. It is desired to provide a passive magnetic bearing with an additional separating force between journal and bearing members to provide support between these parts and to minimize contact between these parts and thus minimize breakdown of these parts. It is further desired to provide a product filled clearance gap which will provide damping. It is desired to provide clearances designed relatively large to allow larger particles to pass through without damage to the bearing.
It is further desired to provide an assembly for use in substantially all sealless pumps such as in canned motor pumps and in magnetic drive pumps with operating temperatures such that the Curie temperature of the magnets is not exceeded.
It is desired to provide a device which is useful for minimizing the deformation of the container walls due to pressure differential across the container walls of the magnetic bearings, and for maintaining a uniform bearing concentricity and a uniform clearance gap for fluid flow between journal and bearing members.